Airship envelope



AIESI-II? ENVELOEE.

No Drawing.

To all whom it may concern:

Be it known that l, LUnwIe Donn, a cit izen of Germany, residing at i riedrichshafen, Germany, have invented certain new and useful improvements in Airship Envelopes, (for which I have filed application in Germany July 2 .5. 1914,) of which the following is specification.

My invention refers to airship envelopes and more especially to a novel manner of ranging; said envelope on the airship body, such novel envelope allowing of obtaining an increase in the travelling speed of the airship.

As is well known, at the surfaces of the body of an aerialvehicle, owing to its moving through the air, on the one side an increased pressure and on the other side a re duced pressure prevails. Now, in the case. of an absolutely impermeable surface the air will pass along the body without exerting upon its surface any other effect than such increased or reduced pressure. W ith bodies having a permeable surface things are entirely different. At those portions of the surface which are placed under increased pressure, part of the air ill enter the interior of the body through the envelope, whereas at those places, where a reduced pressure prevails, the air will tend to escape from the interior outwards. Obviously the flowing of air from outside towards the interior andvice versa consumes mechanical energy which is however spent quite uselessly and which does not therefore assist in the propulsion of the vehicle.

It is true that this disadvantage does not arise when the surface is impervious to air, but a surface of this latter kind involves considerable disadvantages of a different kind as compared with a permeable surface. An impervious surface can be obtained only at the expense of a very considerable increase in weight, a circumstance which, as is well known, plays a great roll in aerial navigation. Furthermore the manufacture of an impervious surface and the production of envelopes therefrom is far more expensive.

According to the present invention now, I have succeeded in combining as far as possible the advantages of the impervious and Specification of Letters Eatcnt.

Application filed June 28,

Patented Apr. 4:, 1922.

1920. Serial No. 392,540.

the permeable surfaces. My investigations and practical tests carried out with the aid of model bodies have shown that those places 'of the body where a considerable increased or reduced pressure prevails, are small as compared with the total surface of the body and, more especially in the case of airship bodies, are far less than one half of the total surface. These relatively small portions now, which, if composed of a permeable envelope, would be the cause of considerable reductions in speed, are provided in accordance with the present invention with an impervious surface, while all the rest of the body of the aerial vehicle is covered with apermeable envelope which is at the same time lighter and cheaper.

As is well known, the central portion of an airship body has a substantially cylindrical form which is reduced towards the forward and rear ends to a more or less rounded point. Now these points whose length varies somewhat in accordance with the particular section of the airship and forms up to about the fourth part and even more of the total length of the ship, the forward point resembling approximately a rotation ellipsoid or paraboloid, while the rear one resembles a cone form, as has been ascer- EN, GERIVIAEY, .diSSIG-NOB T0 LUFTSCHIFEBAU All HAFTUNG, 3F FRIEDEIOHSI-IAFEN,

tained by tests, are the places of considerable fabric or the like impervious to air, while the large central portion of the airship body is covered with an envelope permeable to air in so far as at this portion, owing to the cylindrical form of the envelope, no cpnsiderable increased Or reduced pressure will be apt to arise.

By the arrangement aforesaid by far the greater part of the energy consuming passage of air through the envelope is obviated and nevertheless the greater part of the surface of the airship body can be provided with the light permeable surface. Now, although at this permeable surface a slight passage of air will still take place, at these places of low increased or reduced pressure the influence of such passage is rather useful inasmuch as the smaller eddies which might form at this surface, owing to ircraft, and permeable to air at the other places.

2. An airship comprising an envelope consisting of a material impervious to air near the points and of a material permeable to air at the central portion of its body.

In testimony whereof I afiix my signature.

LUDWIG DURR. 

